I want to make queue with ten requests, and I want to load it in order.
How can I do it? Have you any ideas?
ASINetworkQueue runs all the requests in the order they were inserted into the queue. It is a first in, first out (FIFO) system.
If you want to ensure they all get run one after another rather than in parallel then you can set the concurrency to 1. The queue will start from the first request and run it one by one until it gets to the last request
ASINetworkQueue *networkQueue = [[ASINetworkQueue alloc] init];
// Here we add all our 10 requests, the order in which we add
// them determines the order they will execute
// Set the concurrency to 1 and fire off the queue
[networkQueue setMaxConcurrentOperationCount:1];
[networkQueue go];
Check AFNetworking as ASIHTTPRequest is not maintained anymore. You can use it with NSOperationQueue, which hast the property maxConcurrentOperationCount. If you set this to 1:
Setting the maximum number of operations to 1 effectively creates a serial queue for processing operations.
NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:#"https://gowalla.com/users/mattt.json"]];
AFJSONRequestOperation *operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {
NSLog(#"Name: %# %#", [JSON valueForKeyPath:#"first_name"], [JSON valueForKeyPath:#"last_name"]);
} failure:nil];
NSOperationQueue *queue = [[[NSOperationQueue alloc] init] autorelease];
[queue setMaxConcurrentOperationCount:1];
[queue addOperation:operation];
[queue addOperation:anotherOperation];
Related
I have an HTTPClient request as follows :
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:urlStringMain]];
AFHTTPClient *httpClient = [[AFHTTPClient alloc] initWithBaseURL:url];
NSDictionary *params = [NSDictionary dictionaryWithObjectsAndKeys:
//parameters
nil];
[self beginBackgroundUpdateTask];
[httpClient postPath:postPath parameters:params success:^(AFHTTPRequestOperation *operation, id responseObject) {
//id results = [NSJSONSerialization JSONObjectWithData:responseObject options:NSJSONWritingPrettyPrinted error:nil];
//completion code
[self endBackgroundUpdateTask];
} failure:^(AFHTTPRequestOperation *operation, NSError *error) {
//failure code
}];
[httpClient release];
The background task is executed in :
- (void) beginBackgroundUpdateTask{
[operationQueue addOperationWithBlock:^{
NSLog(#"started upload process as a background job");
self.backgroundUpdateTask = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^{
[self endBackgroundUpdateTask];
}];
}];
}
And ended in :
- (void) endBackgroundUpdateTask{
NSLog(#"complete upload process as a background job");
[[UIApplication sharedApplication] endBackgroundTask: self.backgroundUpdateTask];
self.backgroundUpdateTask = UIBackgroundTaskInvalid;
}
where self.backgroundUpdateTask is a UIBackgroundTaskIdentifier object, and operationQueue is an object of NSOperationQueue (public member), initialized in viewDidLoad:
operationQueue = [[NSOperationQueue alloc] init];
[operationQueue setMaxConcurrentOperationCount:NSOperationQueueDefaultMaxConcurrentOperationCount];
Now what I want to do is, perform these requests chronologically, in the background, such that pushing/popping from the viewController does not affect the request. It should also not be affected if the application goes into background. At times I post text, and at other times I post an image. Now, images take longer to upload, than text so if subsequent requests of text and images are made, texts are posted first, and images later. This breaks the chronology of the tasks, hence I wanted to use the NSOperationQueue. But being new to operation queues, I cannot seem to make it work. The chronology is still not being respected. How do I perform the task in the way I want to.
PS. Also, as you can see in the code, i have added [self endBackgroundUpdateTask] in both, the completion block of the httpClient request, and the beginBackgroundUpdateTask method. Now i understand this is not good. Where exactly should the endBackgroundUpdateTask method be called ?
Thank you.
The HTTPClient can handle the background task for you if you ask it to, simply set the appropriate flag (you need to create the operation and call setShouldExecuteAsBackgroundTaskWithExpirationHandler:).
Rather than change how the uploads operate, keep it simple. Send a date with the upload and use that to maintain your order information on the server.
If you really must execute your operations serially then you can get the operationQueue from the client and set it to only execute a single operation at a time.
In either case you shouldn't need to create your own operation queue.
I'm trying to queue up some TWRequest calls using NSInvocationOperation. It seems to add the method calls in the correct order, but the doSomething: methods get called at the same time pretty much, ie run concurrently, rather than one after the other, which is what I want to achieve.
In addition, the complete in the wrong order, which suggests it's not running one after the other...
- (void)prepare {
if(!self.queue){
self.queue = [[NSOperationQueue alloc] init];
[self.queue setMaxConcurrentOperationCount:1];
}
for(NSString *text in calls){
NSLog(#"Adding to Queue... %#", text);
NSInvocationOperation *indexOperation = [[NSInvocationOperation alloc] initWithTarget:self
selector:#selector(doSomething:) object:text];
[self.queue addOperation:indexOperation];
}
}
- (void)doSomething:(NSString*)someText {
TWRequest *request = [[TWRequest alloc] initWithURL:[NSURL URLWithString:#"http://something.com"] parameters:nil requestMethod:TWRequestMethodGET];
NSLog(#"About to Perform Request... %#", someText);
[request performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error)
{
dispatch_sync(dispatch_get_main_queue(), ^{
// works fine
NSLog(#"Network Finished... %#", someText);
});
}];
}
In the log I see this:
2011-12-30 18:34:34.553 app[32745:10703] Adding to Queue... 1
2011-12-30 18:34:34.555 app[32745:10703] Adding to Queue... 2
2011-12-30 18:34:34.556 app[32745:10703] Adding to Queue... 3
2011-12-30 18:34:34.557 app[32745:13e03] About to Perform Request... 1
2011-12-30 18:34:34.560 app[32745:13e03] About to Perform Request... 2
2011-12-30 18:34:34.563 app[32745:13e03] About to Perform Request... 3
2011-12-30 18:34:35.303 app[32745:10703] Network finished... 3
2011-12-30 18:34:35.454 app[32745:10703] Network finished... 2
2011-12-30 18:34:35.601 app[32745:10703] Network finished... 1
I'm expecting to see (2) to Perform Request after (1) has finished etc... Any pointers?
The operation queue is working fine. As #Joe said in the comment, performRequestWithHandler: starts an asynchronous connection and returns immediately. You can see this by adding an NSLog to the end of doSomething as follows:
- (void)doSomething:(NSString*)someText {
TWRequest *request = [[TWRequest alloc] initWithURL:[NSURL URLWithString:#"http://something.com"] parameters:nil requestMethod:TWRequestMethodGET];
NSLog(#"About to Perform Request... %#", someText);
[request performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error)
{
dispatch_sync(dispatch_get_main_queue(), ^{
// works fine
NSLog(#"Network Finished... %#", someText);
});
}];
NSLog(#"doSomething Finished");
}
To have each request happen serially you need to either make the request synchronous within the operation (use the signedRequest method and a synchronous NSURLConnection) or don't use an operation queue and invoke the next request in the completion handler of the current request. Keep in mind that if you use an operation queue the order in which operations are performed is not based on the order they are added. You might consider using GCD directly with a serial dispatch queue.
I'm successfully making a ASIFormDataRequest using the below code.
//get groups
if (![self queue]) {
[self setQueue:[[[NSOperationQueue alloc] init] autorelease]];
}
//make the url by appending the URL from the Constant class to the jsp name
NSURL *url = [NSURL URLWithString:[NSString stringWithFormat:#"%#/%#", URL, #"connectors/searchGroupsServlet.jsp"]];
ASIFormDataRequest *request = [ASIFormDataRequest requestWithURL:url];
[request addRequestHeader:#"User-Agent" value:USER_AGENT];
[request addPostValue:[login username] forKey:#"username"];
[request addPostValue:[login password] forKey:#"password"];
[request addPostValue:[searchText lowercaseString] forKey:#"query"];
[request addPostValue:GROUP_FILTER_LIMIT forKey:#"limit"];
[request setDelegate:self];
[request setDidFinishSelector:#selector(requestDone:)];
[request setDidFailSelector:#selector(requestWentWrong:)];
This request is currently made on every key press a user makes in a searchbox (The text typed is sent off in the request as the search string). However, rather than sending the request on every key press, I want to delay the request by a second to allow users to type further characters into the searchbox before the request is sent.
I've successfully made a thread that waits a second as users continue to type (although admittedly Im not convinced this is the best way to do it yet, but it works for now)...
this
[self performSelectorInBackground:#selector(wait:) withObject:request];
calls this
-(void)wait:(NSString *)request
{
[NSThread sleepForTimeInterval:1.00];
[[self queue] addOperation:request]; //queue is an NSOperationQueue
}
but, if a user continues to type, I haven't managed to work out how to cancel the request or not put the request in the queue, or empty the queue and replace it with the new request.
Finally, obviously I could force users to wait until they have pressed the 'search' button on the pop-up keyboard, but I was hoping to provide search results without that.
Thanks
The answer was to create an NSTimer, and invalidate it whenever a new key press had been made. Then start it again.
[timer invalidate];
You can try this to cancel
+ (void)cancelPreviousPerformRequestsWithTarget:(id)aTarget selector:(SEL)aSelector object:(id)anArgument
Hey! I need to know how I can have my iOS Application start a download in the background of the application (like, have the download run in the AppDelegate file) so changing ViewControllers will not interrupt or cancel the download. I also need to be able to get the progress of the download (0.00000 - 1.00000), to set a UIProgressView object to, which also means I need a - (void)progressDidChangeTo:(int)progress function.
Just use ASIHTTPRequest it is way easier than NSURLRequest and does exactly what you need.
It examples that shows how to download in background and how to report progress.
I wouldn't download anything in the AppDelegate directly. Instead I would create a separated class just for that purpose. Let's call it MyService I would then initialize that class in my app delegate.
The class can work as a singleton or can be passed to each view controller that requires it.
In MyService class I would add the ASINetworkQueue and few methods to handle the requests when they are ready. Here is the code from ASI examples that you can use:
- (IBAction)startBackgroundDownloading:(id)sender
{
if (!self.queue) {
self.queue = [[[ASINetworkQueue alloc] init] autorelease];
}
NSURL *url = [NSURL URLWithString:#"http://allseeing-i.com"];
ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:url];
[request setDelegate:self];
[request setDidFinishSelector:#selector(requestDone:)];
[request setDidFailSelector:#selector(requestWentWrong:)];
[self.queue addOperation:request]; //queue is an NSOperationQueue
[self.queue go];
}
- (void)requestDone:(ASIHTTPRequest *)request
{
NSString *response = [request responseString];
//Do something useful with the content of that request.
}
- (void)requestWentWrong:(ASIHTTPRequest *)request
{
NSError *error = [request error];
}
If you need to set the progress bar. I would just expose the setDownloadProgressDelegate of ASINetworkQueue in my MyService class and set it in my ViewControllers like that:
[[MyService service] setDownloadProgressDelegate: self.myUIProgressView];
BTW. If you need to continue downloading even when your app exits you can set ShouldContinueWhenAppEntersBackground property of your request to YES.
you can use NSURLConnection to start an asynchronous request that won't cause your UI to be frozen. You can do it by doing something like:
NSURLRequest *urlRequest = [[NSURLRequest alloc] initWithURL:url];
connection = [[NSURLConnection alloc] initWithRequest:urlRequest delegate:self];
[urlRequest release];
in order to have your progress you can use the:
connection:didReceiveResponse:(NSURLResponse *)response;
delegate call to inspect the response.expectedContentLength and then use the
connection:didReceiveData:(NSData *)data
to track the amount of data that was downloaded and calculate a percentage.
Hope this helps,
Moszi
Hi I am trying to create a NSOperaion Queue to download a bunch of PDF files. But it doesnt work. The delegate methods dont get called for NSURLConnection since i put them in NSOperation queue.... any alternatives or solution???
- (void) loadData {
NSOperationQueue *queue = [NSOperationQueue new];
NSInvocationOperation *operation;
for(int i=0;i<[self.pdfArray count];i++){
NSString *url = [NSString stringWithFormat:#"http://www.somelink.com/%#.pdf",[self.pdfArray objectAtIndex:i]];
operation = [[NSInvocationOperation alloc] initWithTarget:self
selector:#selector(loadDataWithOperation:)
object:url];
[queue addOperation:operation];
[operation release];
}
}
- (void) loadDataWithOperation:(NSString *) url{
// Create the request.
NSURLRequest *theRequest = [NSURLRequest requestWithURL:[NSURL URLWithString:url]
cachePolicy:NSURLRequestUseProtocolCachePolicy
timeoutInterval:60.0];
NSURLConnection *theDownload = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self startImmediately:YES];
}
take a look here, this is a tutorial that was helpful to me so I bookmarked it
http://www.dribin.org/dave/blog/archives/2009/05/05/concurrent_operations/
I can't really see a problem with the code but it might be a threading issue. NSOperationQueue creates a thread through Grand Central Dispatch to run the operation. If NSURLConnection then also tries to create a thread it might cause an issue - I'm not sure a thread can be a child of a child thread.
You could do an sendSynchronousRequest: so that it stays in the thread that you have created in the NSOperationQueue and see if that works better.
NSURLConnection needs a running NSRunLoop to function. If you call NSURLConnection methods on a thread whose NSRunLoop is not running, the NSURLConnection will never run. The worker threads that NSOperationQueue creates don't have their NSRunLoops running. Nor could you guarantee that the thread would still exist when the NSURLConnection received a response from the server.
It is fine to call NSURLConnection methods from a background thread, but it needs to be a thread whose lifetime you can guarantee and it needs to have its NSRunLoop running.